function allvehs = get_allvehs(fieldTestNumber)

% input:
%   fieldTestNumber - the number of the field test
%       1: June 30 in Berkeley
%       2: July 16 in Berkeley
%       3: July 28 in Berkeley

% output
%   allvehs - M-by-4 matrix where M is the total number of trajectory
%       points for all vehicles.  The 4 columns are vehicle number (not the
%       same as the number on the phone), time in seconds from the
%       beginning of the day of the test, latitude, longitude

filename = ['field_test_' int2str(fieldTestNumber) '/allvehs.mat'];
if ~exist(filename,'file')
    error('file does not exist');
else
    load(filename);
end